Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$91.27	9.694%	$100.1177	$100.12	$100.10	$100.10
Purchase #2	$142.89	4.259%	$148.9757	$148.98	$149.00	$149.00
Purchase #3	$157.28	6.396%	$167.3396	$167.34	$167.35	$167.30
Purchase #4	$198.29	8.184%	$214.5181	$214.52	$214.50	$214.50
Purchase #5	$86.71	12.744%	$97.7603	$97.76	$97.75	$97.80
Purchase #6	$219.35	10.581%	$242.5594	$242.56	$242.55	$242.60
Purchase #7	$39.49	10.234%	$43.5314	$43.53	$43.55	$43.50
7 purchase totals =	$935.28		$1,014.8022	$1,014.81	$1,014.80	$1,014.80